Added source browser

Added a SourceLister class, which enumerates all DVD folders below a given starting directory.
Added a source browse page to list the available sources

pages/browse/sources.php

@@ -0,0 +1,10 @@
+<?php
+
+$main = HandBrakeCluster_Main::instance();
+$config = $main->config();
+
+$lister = new HandBrakeCluster_Rips_SourceLister($config->get('rips.source_dir'));
+
+$this->smarty->assign('sources', $lister->sources());
+
+?>